Method of forming coaxial cables



Dec. 14, 1948. L. H. MORIN METHOD OF FORMING COAXIAL CABLES F lm April 25,. 1944.

N ix 7// llllllllllllIlHllHiiifi II llllll llll .lou/s (fllmllll I n NVE /-/ Mom/v ATTORN Patented Dec. 14, 1948 UNIT-ED STATES PATENT OFFICE Marnon or :FQRMING CQAXIAL CABLES Louis .H. Morin-, Bronx, N. Y. a lieatiennpril-sa 1944, ISerialrNo. $532,660

This invention deals with the formation -.-.0f elongated die cast bodies, such for tex-aniple as elongated insulator :members between conductors of a coaxial cable. -Mor e particularly, the inventionrelates to a methodwhich comprises'forming an elongated die'castgloooly of the class defined l xa successive seriesof individual casting operations, and in such -;rnann-er as toi1orm .acontinunus integral body in the {resulting =-elongated "die castxmember. specifically, in the illustrated disclosure, in the formation of a spiral or helical insulator directly upon *and ;as an integral :part of an elongated conductor. Thus, from :this standpoint, :the method comprises the vfeeding of ra conductor strand intermittentlythrough a casting station in such manner as to ;-form in a successive series of 'v-intermittent casting operations a continuous spiral ;or h-elix'on said conductor. The novel ifeatures of the invention will be ibest mnderstood from :the following description "when taken toether with the accompanyingdrawinsin which certain embodiments of the invention aredisclosed, and-in which :theseparatepants are designated i by suitable reference. characters vin .eac-h of the views, and in which: Fig. ;1=-is a-di-agrammatic sectional -;;view of a machine employed [for carrying .-r-n y improved methodlinto effect.

i Fig. 2 is an enlargeddetail vi-ewnofla part Qffi conductor with a helical insulator :thereon, and also; diagrammatically show-ingmart of the :feeder mechanism. 1

.Figs. :3 and-i4 are views:similarpto;EigJZyShow ingzthe operationsof the feeder mechanism.

Fig. 5 ,is a diagrammatic cross sectional-view through a vcoaxial cable made iaccordingato my improved method; and

Fig. '6 is .a sectional detail view of .a vpart of the construction shown in Fig. -1, and showing gamedification.

In the conventional method ;of ;procedure, in

forming die castings, it has "been "thecommon I practice tolinj ect casting material 'intozthelcauiti or impression of relativelymovabledieswtodorma casting, then to separate 'the'dies and remove the casting from the-cavity-or impression-and then to again close the diesandat-oforml-the,nextlsuc cessive and independent casting.

With my presentmethodvhowever, atotall-y castinsmperations sin impressions .QrLcavities of Furthen'the i-nyentionqdeals more member is .formed, substantially as though the entire elongated member had been formed in a single .castingoperation Furthermore, the present :method deals --with forming elongated .-die cast bodies of irregular contour, such for example, .as .aspiral or helix wherein the method comprises rotation of the die in each injection stroke :of the machine or during each casting-operation; The methodmay also include the use .of supplemental, dies movable relatively to the lworkpiece and-the first named die i i-or .torniing other integral ringv like members at spaced intervals alon the spiral or helix, as diagrammatically illustrated in Fig. ;6;of the dr in i i w 1 :In the accompanying drawing, and for the purpose-cf illustrating .oneadaptation and use of the invention, I jhave "illustrated the method as applied to the formation-of plastic castings from thermoplastic materials, and still more particularly in the formation of coaxial cables in which the spiral orrhelical plastic insulator is first formed .upona conductor strand, after which an outer conductor isga-rranged upon the helicalor spiral insulator and then finally casings or jackets of insulatinggmaterial are disposed aroun the -;outer conductor. l -While any type of casting materials maybe employed informing elongated'die cast bodies in accordance with-my method,-the presentillustra V "In Fig. 1 of the drawingonly such parts of the machines ofythe kind disclosed in said-patents :is show-ngas 'ttO enablethe presentmethod to be understood. The casting mechanism of the .ma- Qhineiisjgencrallyshown at :10 in Fig. lot the drawin Whereasthe feeder mechanism of the prises a hopper l2 for the reception of powdered or granular plastic material. At the bottom of the hopper is a slide l3 having a measuring aperture I4 therein which measures the quantity of plastic material delivered in each stroke to the discharge chute l5 which. is arranged overthe funnel like member l6 arranged directly above the admission aperture ll into the cylinder l8. The slide l3 has a depending arm 19 coupled with the outer end 26 of the tubular plunger, which plunger is actuated through the bell crang' mechanism generally indicated by the reference 2!. It will thus be seen that in the forward stroke .of the plunger, the slide I3 is also moved'forw'ardly.

The plastic material delivered into the funnel IS in the forward stroke of the slide 13 drops upon the forward reduced end 22 of the tubular plunger and in the retracted movement of the plungeiy to the position shown inFig. 1 'of the drawing, this material then drops into the cylinder in position to be advanced in the nextinjection stroke. The quantity admitted into the cylinder is sufficient to format least a single casting.

At 23 is diagrammatically illustrated the heating coil at the discharge end of the cylinder [8 for heatingthe plastic material in the cylinder, and this coil is automatically controlled to regulate the required temperature, as is known in this art. Arranged at thedischarge end of the cylinder is a die 24, the die being mounted in the offset portion 25 of a die holder 26, this holder having a flange portion 21 adapted to bear against a ball thrust bearing 28 supported between suitable plates29 and 30. Thepurpose'of this constructionis 'to provide free rotation of the holder 26 as well'as the die 24 mounted therein. To simplify the construction of the die 24, it may be composed of separate parts, each part being secured to the holder 26 by screws 3|. The die 24 has formed therein an impression or cavity 32 fashioned to receive a conductor 33; and to form around the conductor a portion of a'continuous spiral or helical member, as more fully hereinafter set forth. The length of the spiral or helix in the die 22 is substantially equal towhat might be considered a complete turn. a v

Itwill, of course, be understood'thatthe'die holder will be water cooled,- as in conventional machines of this kind in order to chill the casting material, but this has been omitted in the present diagrammatic illustration, as in itself, it for'ms no part of the present invention.

The feeder mechanism H feeds the conductor including the helical insulator 34 thereon from right to left, as appearing in Fig. 1 of the drawing. The feedermechanism comprises an elongated tubular shaft'35, atone end of which is an elon gated pinion 36 which meshes with the gear 3? arranged'upon one end of ashaft 38. -At the other end of theshaft is a ratchet wheel 39 which is intermittently rotated by suitable mechanisms in the machine a quarter revolution in imparting one-revolution to the shaft'35. v

Supported in connection with the end of the shaft adjacent the die 24 are radially movable mounted on the shaft 35. The sleeve 43 has a grooved end portion 44 adapted to be engaged by a yoke shaped lever 45 suitably operated in the machine to move the sleeve 43 to the right in moving the jaws 40 into their gripping position, as will be apparent.

The shaft 35 is supported in a slide 45, mounted to move back and forth in the machine with respect to the die 24, a suitable link 41 being coupled with operating mechanisms of the machine in performing this operation timely with 1 the operation of the plunger 23.

'In Fig. 6 of the drawing is shown a slight modification. In this figure, 48 represents a die which differs from the die 24 simply in having an annular recess49 in the outer surface thereof, which recess is interrupted solely by the passages 53 inthe die which form the helix or spiral 5| on the conductor 52. The helix or spiral differs from the helix or spiral 34 in that it includes at spaced intervals the collars or sleeve portions 53 which are partially formed by the recess 49. The re mainder of the collars are formed by the recess or cavity 54 in two supplemental die members 55 and 55, which are movable toward and from the conductor 52 over the outer surface of the die 48. These supplemental dies 55 and 56 will also include cavity portions conforming with the spiral or'helix 5i, as will clearly appear from a consideration of Fig. 6 of the drawing. At 51 is shown the discharge end of a cylinder similar to the cylinder Hi. "In producing coaxial cable, it will be understood that after the conductor 33 with its helical insulator 34 thereon or the conductor 52 with the helix 5| thereon passes from the feeder mech anism, the outer conductor 58 may be applied upon the helical insulator 34 and 5| and this conductor then covered or enclosed in insulator jackets 59 of fibrous or any other suitable material, depending entirely upon the type and kind ofcoaxial conductor or cable which is produced. In the present illustration, the conductor 33, as seen in Fig. 5 of the drawing is shown as a solid rod or' wire, however, in some instances, this conductor is tubular.

To rotate the die holder 25, the flange portion 21 has on the periphery thereof gear teeth 50 adapted to be engaged by a gear 6!, note Fig. 1. The gear 60 and the means for rotating it are only partially shown, but would be the same as the means disclosed for rotating 'a substantially similar gear in the companion application Serial No'. 532,659 filed of equal date herewith now Patent No. 2,446,059. The gear Bl is intermittentlyrotated in the operation of drawing the conductor 33 through the die cavity 32 so as to allow the die 24 to rotate around the cast helix. This method of rotating the holder 26 is primarily applicable to structures as seen in Fig. 6, where the supplemental dies 55 and 56 are arranged upon the outer surface of the die 48. In struc- 34 in: the die 24. The sleeve 43 is then moved 4 to the left to release the jaws 4 11-, which are then this operation, the plunger has been moved to the right, assuming the position similar to that shown in Fig. 1 of the drawing, after which the powdered or granular plastic material which had previously been deposited in the funnel ll; will drop into the cylinder ill in front of the end 22 of the plunger. During the above operation. the cast section or unit of the spiral or helix 34 remains stationary in the die 24.

The machine is now ready for the next operation which can be regarded as the casting or injecting operation. The sleeve d3 is now moved to the right on the shaft to force the jaws Ml inwardly into firm gripping engagement with the conductor 33. The plunger will now be advanced to move the powdered or granular plastic material to the left in the cylinder I8 to'a point where injection of the heated plastic material at the outer end of the cylinder is to begin. At this moment, the slide 46 is moved to the left, the jaws 40 being firmly supported in the sleeve 43 in this operation. This operation feeds the conductor 33 including the pro-cast section of the spiral or helical insulator 34 to the left and out of the die 24, the die holder 26 being positively rotated in this operation and simultaneously another cast unit or section of the spiral or helical insulator is formed on the conductor, as the plunger 20 is moving forwardly simultaneously with the movement of the slide 46. At the completion of this last operation, the parts will again return substantially to the position shown in Fig. 1, excepting that in Fig. 1, the plunger has been shown in its retracted position, it being understood that pressure is relieved from the casting material immediately upon formation of the cast section as described above.

It will be understood that the above described cycle of operation is automatic and repeated at intervals to form the successive cast sections or portions of the insulator, and the speed of this operation will depend largely upon the amount of material in each unit cast section. However, each unit will be permanentl united with the adjacent unit so as to form a continuous elongated spiral or helical insulator on the conductor. In other words, it will be apparent that the cavity 32 of the die is always exposed to the outer nozzle discharge end of the cylinder l8, and in this sense, the cast insulator 34 may be said to be formed from a plurality of intermittently extruded sections.

The above described operation of the feeder mechanism H is diagrammatically illustrated in Figs. 2, 3 and 4 of the drawing. In other words, the jaws while assuming the position of Fig. 3 are first moved radially, as indicated by the arrow of said figure, and then the jaws move to the right in the manner stated to a position similar to that illustrated in Fig, 4, and are then moved into gripping engagement with the conductor 33, as indicated by the arrow of Fig. 4, after which the jaws are moved to the left, moving with them the conductor and the helix 34 thereon, this movement being from the position shown in Fig. 2 to that illustrated in Fig. 3, and then this cycle of operation is repeated.

The operation of the structure shown in Fig. 6 will be the same as that shown in Fig. 1, with aaeasoa a tion stroke the dies 55 and 56 will be quickly moved into engagement with the conductor 52 and in the final stroke of the pluner casting material will be formed into the cavity recesses i9 and 54 in forming the ring like or sleeve like members 53 which completel encircle the conduc-tor'52.

It will be understood that the complete coaxial conductor or cable may be produced in one continuous operation or may be cared for in a series of operations. The production of the inner conductor with its spiral or helical insulator thereon actually constitutes the formation of a product, I

in a series of intermittent feeds, each feed stroke being governed by the length of the cavity or impression in the die. During this feed stroke, the die is rotated to feed the die around the precast insulator as the casting material is pressure injected into the die cavity so that when the die again comes at rest, the cavity will again be filled, and a new section of the insulator formed. The ball bearing employed provides free rotation of the holder 21, and at the same time, takes up the thrust during the injection stroke of the plunger The method as herein described has been applied to the production of a specific kind of product. This is by way of illustrating one adaptation and use of the invention. In a general sense, the method comprises forming elongated castings from a plurality of independently cast sections which are cast one upon the other in producing said product.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The method of die castin a helically shaped insulator upon a conductor which comprises castin upon a length ofsaid conductor a section of insulating material by injecting said material in the plastic state into one end of a helically shaped cavity of a die through which said conductor extends, simultaneously gripping the conductor between a pair of jaws at a point beyond the other end of said cavity during said casting step, releasing the grip on the conductor after the casting step by opening said jaws, moving the jaws closer to the die while coincidently rotating said jaws about the conductor, regripping the conductor between said jaws, moving the jaws and the conductor away from the die while rotating the latter to pull said cast section out of the die and bring another length of conductor therein, and casting another section of insulating material on the conductor by injecting said material in the plastic state into said die cavity simultaneously with the movement of the conductor therethrough.

2. The method of die casting an elongated helically shaped insulator longitudinally upon a insulating material to a plasticizing chamber to be plasticized, pumping the plasticized material into one end of a helically shaped cavity of a die on which said conductor extends while gripping the conductor between a pair of jaws at a point beyond the other end of said cavity, thereby casting upon a length of said conductor a section of insulating material, releasing the grip on the conductor by opening said jaws, moving the jaws closer to the die while coincidently rotating said jaws about the conductor, regripping the conductor between said jaws, moving the jaws and the conductor with the cast section thereon through and out of the die while simultaneously rotating the die, thereby moving into said cavity a succeeding length of said conductor, feeding another charge of insulatin material to said plasticizing chamber to be plasticized, pumping plasticized material coincidently with said last moving step into the cavity of said die so as to form a second cast section upon said conductor, halting the conductor after said last-mentioned pumping step to permit said second cast section to become united with said first-mentioned cast section in end-to-end relationship, and repeating the above described method to form on the conductor an elongated length of insulating material.

3. Themethod of forming an elongated helically shaped die cast member which comprises intermittently injecting heated casting material into the registering cavities of a first rotatable die and a second die relatively movable to said first die so as to form successive cast sections of said material, each section being united to the preceding section; said dies abuttin each other and each havin a helically shaped cavity extending therethrough and an annular recess in their abutting surfaces for forming a ring like member on each said cast section; intermittently opening said second die by moving it relatively to said first die and away from a cast section formed 1 therein, and intermittently discharging each said cast section from the first die coincidently with the injection of heated casting material thereto, said discharging operation being performed by intermittently rotating said first die during the discharge of each said cast section; and intermittently closing said second die substantially at the completion of said last-mentioned injection step but in time to have heated casting material forced into the cavity thereof.

LOUIS H. MORIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 724,287 Heilmann Mar. 31, 1903 1,577,336 Marsden Mar. 16, 1926 1,706,728 Daniels Mar. 26, 1929 1,824,482 Hartmann Sept. 22, 1931 1,845,249 Derby Feb. 16, 1932 1,929,395 Barton Oct. 3, 1933 2,127,857 Bond Aug. 23, 1938 2,226,048 Weaver Dec. 24, 1940 2,348,172 Taylor May 2, 1944 FOREIGN PATENTS Number Country Date 16,542 Great Britain July 18, 1912 401,428 Great Britain Nov. 16, 1933 445,852 Great Britain Apr. 17, 1936 

